The present invention relates generally to networks. More particularly, the present invention relates to the deployment of a carrier's carrier (CsC) substantially without directly exchanging customer routes, or advertising next hops, between customer edges (CEs).
A virtual private network (VPN) created using multiprotocol label switching (MPLS) generally allows CEs, which may be routers, to communicate with a provider edge (PE), which may also be a router. A CE is typically located at the edge of a customer network, and is in communication with a PE of a service provider of an MPLS network. Customer routes between the CE and the PE are generally stored in a VPN routing and forwarding table (VRF) of the PE. The storage of all customer routes associated with a CE into a VRF of a PE allows the PE to locate a suitable route over which to route a received packet to a customer. However, the storage of all customer routes associated with a CE into a VRF is resource-consuming, particularly when a CE has a relatively large number of associated customer routes. Storing customer routes in VRFs is relatively expensive, and may utilize significant system resources, e.g., consume a relatively large amount of the memory space in the VRF.
A CsC architecture allows for the direct exchange of customer routing states between CEs. That is, a CsC architecture allows routes to be exchanged directly between customers, and also advertises routes with labels so as to create label switched paths (LSPs) to next hops. In a CsC architecture, a customer builds a mesh of CE-to-CE border gateway protocol (BGP) sessions that carry or otherwise propagate customer routes between the CEs and therefore the CE need only communicate the routes used as next-hops for these directly exchanged routes to the PE. As will be understood by those skilled in the art, building BGP sessions may be relatively expensive in terms of operational complexity for the provider of the CsC service.